A charger capable of safely charging an apparatus even when the current limit value of an external power supply is less than the maximum charging current of the charger or when the battery voltage is low. Charger 100 has backup charging circuit 160 that performs charging using a current that is less than the charging current of charging control section 120. Control circuit 170 performs control so that charging control circuit 123 of charging control section 120 fixes charging control transistor 121 to OFF, makes backup charging circuit 160 operate, and performs backup charging using minute current Ichsub when battery voltage Vb is lower than predetermined value Vbx1, and fixes control transistor 111 of DC/DC converter 110 to ON when supply voltage Vc is less than a first supply voltage value.